DESCRIPTION: The applicant intends to explore the relationships between the sound-induced vibrations of the basilar membrane and the corresponding electrical activity in inner hair cells and spike activity in the auditory nerve. Most of the specific tasks will be carried out in chinchillas and will be aimed at observing the mechanical origins of frequency-specific nonlinearities of auditory-nerve responses to sound. Instruments that allow detection of vibrations of atomic dimensions will be used to record basilar-membrane responses to various acoustic stimuli. Responses to the same stimuli will be recorded intracellularly from inner hair cells and from single auditory-nerve neurons. In a second project, the applicant intends to observe the course of maturation of basilar membrane function in a late-maturing rodent-- the Mongolian gerbil. The proposed investigations are intended to help understand the process of mechanical-to-neural transduction in the human ear (which the ears of chinchillas and gerbils resemble), which presumably will be important in specifying possible mechanical aspects of pathology in human deafness.